Need of data exchange between different graphic data processing systems, such as CAD systems or CAM systems, has increased with the spread of CAD systems, CAM systems and computerized communications brought about by the development of personal computers. The efficiency of data conversion must be enhanced to promote data exchange, because graphic data processing systems are practiced in diversified forms.
Generally, the conventional graphic data conversion method exchanges graphic data indirectly between different graphic data processing systems through an intermediate data file, in which graphic data of one of the associated graphic data processing systems is translated into an intermediate data file, and then the intermediate data file is translated into graphic data capable of being processed by the other graphic data processing system.
Such a conventional graphic data conversion method employs an intermediate data file specified in IGES (Initial Graphics Exchange Specification) of the ANSI Standards or other intermediate data file. Since priority is given to flexibility in designing the data file format of IGES, a series of CAD/CAM records and data is divided into sections. That is, the connection of the divided CAD/CAM data can be expressed only by means of pointers. Accordingly, in converting the CAD/CAM data, the reader must take the trouble to decompose a significant series of records or data into an insignificant series of records or data with pointers. Accordingly, the writer must interpret the significance of the arrangement of a series of records or data after analyzing the pointers to convert the records or data. There will not be any particular problem in such a procedure when the significance of the arrangement of the CAD/CAM records or data is simple, but serious problems arises in such a procedure when the significance of the arrangement of the CAD/CAM records or data is complicatedly hierarchized, and hence accurate data conversion is very difficult. Furthermore, even if the significance of the arrangement is simple, the description of the intermediate data file becomes redundant and a large number of pointers reduces the efficiency of data conversion greatly. Moreover, the intermediate data file of IGES has drawbacks that all the essential elements of CAD/CAM graphic data are not included in the intermediate data file and the ambiguous definition of formats and rules is likely to cause wrong interpretation.
Generally, translators are organized through the data file of IGES in exchanging data between different CAD/CAM systems. However, the functions and quality of the translators vary widely due to the foregoing drawbacks of the intermediate data file of IGES. Thus, the intermediate data file of IGES cannot be the only intermediate data file common to both the different CAD/CAM systems, and hence IGES merely formal standards. Accordingly, in most cases, limited converting functions are defined according to the purpose of conversion, and then an individual intermediate data file is prepared to organize translators.
In either conventional graphic data conversion method, the general applicability and flexibility of the form and rule of the description of the intermediate data file are insufficient, not simple and unperspicuous, and hence it is very difficult to organize a perfect translator. Consequently, the range of conversion is limited and modes of conversion increase in a geometric progression with the increase of the objective different graphic data processing systems or it is impossible to achieve the unrestricted exchange of data connecting graphic forms and their attributes between general-purpose CAD/CAM systems and a series of CAD/CAM systems for automated design, material estimation or production design.
It is an object of the present invention to provide a simple, perspicuous, highly flexible and highly universal graphic data conversion method capable of carrying out unrestricted conversion of graphic data including data connecting graphic forms and their attributes.